Process and a aparatus for production of multilayer trim elements for vehicles

ABSTRACT

Panels and elements for vehicle interiors are obtained by co-extrusion or co-lamination of a layer ( 10   a ) of themoplastic support material containing a reinforcement filler with a layer ( 9   a ) of thermoplastic covering material containing an amorphous thermoplastic and by thermoforming the resulting sheets in a press.

FIELD OF THE INVENTION

The present invention relates to a method and a plant for the productionof multi-layer auto vehicles trim panels in thermoplastic material. Moreparticularly, the present invention relates to a method for theproduction of vehicle interior elements such as, for instance, panels,hatboxes, dashboards, consoles and the like, by thermoformingmulti-layer sheets. The vehicle interior elements thus obtained are alsoan object of the present invention.

BACKGROUND OF THE INVENTION

Thermoformed autovehicles interiors are generally obtained from sheetscomprising a support material and an external covering layer foraesthetic purposes. According to a widely known and used technique, theexternal covering (known as “imitation leather”) is produced separatelyand thereafter joined to the support previously heated in a press. Thepress also provides for the shaping of the panel into the required form.

The support material is generally a polyolefin resin with a vegetablefiller comprising for the most part wood powder. The imitation leatheris generally in PVC and comprises a layer of cotton fabric or othertextile material which acts as a mechanical bonding means for thepolyolefin support.

This technique has several of drawbacks. In the first place, the costand weight of the traditional imitation leather in PVC are both quitehigh. A second problem arises from the costs of the process, whichrequires many steps—some of which are particularly long—such as thecutting of the imitation leather and its positioning on the supportplate. Further problems derive from the anisotropy of the panel asproduced, from the fact that to recycle the waste or the panel at theend of its life it is necessary to remove the imitation leather (PVC)from the support layer (PP), and problems arise from the mechanical andhand (touch) characteristics of the product.

It has been proposed to produce the panels and the vehicle interiorelements by co-injecting the support material and the external imitationleather material. This solution resolves many of the preceding problemsbut is suited to some types of panel only. The European PatentApplication no. 0668142 discloses a method according to which sheetsformed from a support layer and two external covering layers areco-extruded; these sheets are then thermoformed to give trim panels forcars, packing containers and the like. The support comprises polyolefinand an organic filler, particularly cellulose fibers, and the coveringlayers comprise polyolefin and inorganic fillers such as talc andcarbonate. Panels of this type apparently present acceptable mechanicalcharacteristics, but aesthetic and hand characteristics are completelyinsufficient.

DISCLOSURE OF THE INVENTION

An object of the present invention is to solve the above cited problemsby means of a method for producing autovehicles trim panels bythermoforming that is simple, inexpensive and reliable, and that givepanels with good mechanical properties and excellent aesthetic and handproperties.

A further object of the invention is to obtain thermoformablemulti-layer sheets and finished elements having the abovecharacteristics.

Such objects are achieved through the present invention, which relatesto a method for the production of autovehicles interiors and similarproducts shaped by thermoforming, characterized according to claim 1.

According to a preferred embodiment of the invention, support andcovering layers are co-extruded.

According to another aspect of the invention the support layer isobtained by impregnation of two long-fiber needle-punched layers(natural and/or non-woven fabric) with an extruded polyolefin layer;preferably the covering layer is co-laminated on this support. Theinvention also relates to a plant to carry out the method, the plantbeing characterized according to claim 8.

The method according to the invention presents several advantagescompared to known methods in the art. The number of steps and theworking time are greatly reduced, as it is no longer necessary toproduce the imitation leather layer and the support sheets separatelyand then to join them in a press by thermoforming. Materials withidentical or similar bases can be used, for instance PP or polyolefin ingeneral, for both the imitation leather and the support; in this way itis possible to recycle offcuts and production waste. It is no longernecessary to cut the imitation leather and line it up above the supportsheet . The embossing of the imitation leather can take place directlyin the thermoforming mould, which eliminates the problems of loss ofembossing during the thermoforming step and of producing differentembossings in different parts of the panel. Besides, the cost of thematerial is lower; the cost of a imitation leather in PVC is more thandouble that of an imitation leather produced according to the invention.Finally, the resulting panel is more isotropic.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be disclosed in greater detail with reference tothe enclosed non-limiting drawings, in which:

FIG. 1 is a schematic sectional view of a thermoformable sheet obtainedaccording to the invention;

FIG. 2 is a plant layout for co-extrusion of the sheets according to theinvention; and

FIG. 3 is a plant layout for the co-lamination of a sheet according tothe invention.

MODES OF CARRYING OUT THE INVENTION

As mentioned above, the method according to the invention provides forthe preparation of a layer of thermoplastic support material comprisinga filler, the preparation of a covering (skin) material comprising anamorphous thermoplastic material, the binding of the said supportmaterial with said covering to form a substantially flat multi-layersheet, and the shaping of said sheet by thermoforming.

As is well known, an amorphous thermoplastic material is a material thathas no, or substantially no, crystalline content. Examples of amorphousmaterials are PVC, ABS, EVA, TPU and EP(D)M, SBR, SEBS rubbers.Polypropylene (co)polymers can be partially amorphous. The quantity ofamorphous thermoplastic material is between 30% and 100% by weight ofthe covering material and preferably is at least 60% (w/w).

Preferably, the support and covering materials are chemicallycompatible: for instance, a PP based support material with wood powderfiller is used with a polypropylene thermoplastic elastomer imitationleather. As an alternative, a means of chemical or mechanicalcompatibilization, such as for instance stockingette (cotton fabric),can be used. The chemical compatibilization can be obtained by addingcompatibilizing agents such as for instance maleic and fumaric acids,maleic anhydride, metoxysilane, acrylic acids or similar compounds tothe support or the covering materials during the extrusion of same. Afurther way of making incompatible materials compatible is to laminatethem with a film of compatible material: an example is a laminatecomprising a central layer of expanded polyurethane and two externalfilms of PE, PP or EVA. A layer of this type is unrolled from a spooland placed between the material obtained from the two extrusion headsfor the support and the covering to improve the hand of the finalproduct.

FIG. 1 shows a section of a sheet 1 of the type described above,comprising a covering 2, a support 4 and a central foamed layer 3.

In an embodiment of the invention the foamed layer is obtained byextruding it and expanding it with a chemical or physical expander. FIG.2 shows a co-extrusion plant layout comprising two flat-headco-extruders 9 and 10, to extrude the covering material 9 a and thesupport material 10 a respectively. There is also a third extruder 11 toextrude the central layer 3—for instance an expanded layer—between thetwo layers 9 and 10.

The material for the support is a thermoplastic material containing from10% to 80% by weight of a filler that is preferably an organic cellulosefiller, for instance wood powder. If the filler is wood powder, thematerial of the support is obtained preferably by reactive extrusion.This reactive extrusion is obtained by treating a polyolefin, the woodpowder, maleic anhydride and radical initiators in the extruder and wasdisclosed e.g. in European Patent Application no. 96830432.9 in the nameof the applicant. A preferred formulation provides for the use of: homo-and co-polymers of propylene, particularly those with isotactic indexhigher than 30%; between 20% and 60% by weight of a fibrousreinforcement filler, preferably vegetable like wood powder; from 0.05%to 0.5% of peroxide radical initiators, for instance: dicumilperoxide,and 0,2-2,0% of compatibilizator agent of the type mentioned above.

FIG. 3 shows schematically the production of another type of support. Inthis case the support is obtained by passing a layer of polyolefin(preferably PP) and two layers of long-fiber “mats”, through a calender8. The polyolefin is extruded and, while the extruded sheet is still ina partially molten state, it is immediately calendered with the twomats, so that the polyolefin is impregnated and compacted with the mats.Long-fiber mat is here understood to designate those fibrous supportsthat are obtained by needle-punching or equivalent method using fiberslonger than 3 mm and preferably longer than 1 cm. The fibers could bevegetable (jute, flax) or synthetic, particularly non-woven fabric whichin same case is not further needle-punched, for instance when it ishydrobonded.

Preferred fibrous supports are those with long vegetable or mixedvegetable-synthetic fiber, and with weight within the range of 200 to500 g/m².

The material for the covering is a thermoplastic material containing anamorphous polymer material; the quantity of amorphous material isbetween 30% and 100% by weight of the covering material. Preferably, thecover layer is a polyolefin thermoplastic elastomer.

Thermoplastic materials useful for producing the covering are selectedfrom among homo- and co-polymers of alpha olefins such as ethylene,propylene, ethylene-propylene, copolymers of propylene containing one ormore alpha olefin with 2-10 atoms of carbon (for instance ethylene,1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-ottene); EPMrubbers (ethylene/propilene) and EPDM rubbers(ethylene/propylene/diene); natural rubber; EVA (ethylene/vinylacetate);ethylene/1-ottene co-polymer; polyenic home- and co-polimers like thepolybutadiene; styrol/ butadiene rubbers (SBR), hydrogenatedstyrol/butadiene co-polymers (SEBS); acrilo-nitrile/butadiene/styreneco-polymers, their functionalized polymers and their mixtures.

The quantity of EP(D)M rubbers, or their analogues, used is generallybetween 6% and 30% by weight of the total weight of the formulation ofcovering. The rubbers can also be extended with oils (parafin andnaphtene types) to increase the softness to the touch; the quantity ofoil added is between 20% and 60% by weight of the rubber.

The starting thermoplastic material should contain cross-linked andnon-cross-linked compounds and is preferably obtained by reactiveextrusion, i.e. a heat treatment of mixing in the presence of radicalinitiators (preferably peroxides) and compatibilizing agents. Furtherexamples of suitable thermoplastic elastomers for the present inventionare described in Application PCT/EP96/00136 (WO 96/ 22327) in the nameof the applicant. Preferably the covering material will be obtained froma mixture of polypropylene, polyalkenylenes (5-15% in weight), EP(D)Mrubbers (8-40% in weight) and vinylpolybutadienes (0.5-4.0% in weight).

The method for co-extrusion provides (FIG. 2) for the extrusion of thesupport material 10 a, the external covering material 9 a and any insidematerial 11 a through the corresponding extruders 10, 9 and 11. Otherextruders are possible to give further additional layers, or layers ofready material (for instance expanded material) may be unwound from aspool 16. The layers of extruded material in a plastic, i.e. partiallymolten state, are then fed through calender 12 that binds them togetherand imparts the final thickness of the flat sheet 13 that is drawn fromit.

If necessary, the sheet 13 is then heated in continuous oven 15 andcalibrated in continuous press 17; finally, the sheet is thermoformed incontinuous press 14 to give the final product.

In the case of a co-lamination (FIG. 3), first the layer of supportmaterial 7 is extruded, and bonded to mats 6 and 6′, then downstream offirst calender 8, a layer 9 b of covering material is applied to layer 7and, where necessary, a third layer or a material from a spool similarto that described above is used. The multi-layer is calendered throughsecond calender 8 a and thereafter calibrated and thermoformed in a waysimilar to that cited above.

The panels thus obtained present a skin layer (made of the coveringmaterial) that covers all the visible surface of oneside of the same,i.e. the surface that will be the external surface of the panel oncemounted on a vehicle. In the case of a two-layer panel produced withcompatible materials, the imitation leather sticks directly to thesupport layer, in the absence of any physical means of bonding or mutualfixing, such as, e.g. a cotton fabric.

What is claimed is:
 1. A method for the production of autovehicle trimpanels and similar products shaped by thermoforming, characterized inthat it comprises the following steps: providing a layer of supportmaterial comprising thermoplastic material containing from 10% to 80% ofa filler selected from vegetable fibers, wood powder and fiber mats;providing a layer of covering material comprising a thermoplasticmaterial comprising 30% to 50% of an amorphous thermoplastic materialselected from a group consisting of amorphous polypropylene, polyvinylchloride, ABS, EVA, TPU, SBR, EP(D)M, SEBS, rubbers and mixturesthereof; bonding said layer of support material to said coveringmaterial to form a substantially flat multi-layer sheet; and shapingsaid sheet by thermoforming.
 2. A method according to claim 1, whereinsaid sheet is obtained by co-extrusion of said support material (4,10 a)and said covering material (2) in a partially molten state.
 3. A methodaccording to claim 1, wherein said covering material (9 a) isco-laminated on said layer of support material (10 a).
 4. A methodaccording to claim 1, wherein one or more additional layers (3, 11 a,16) are arranged and bonded between said covering and said supportmaterials to provide said multilayer sheet.
 5. A method according toclaim 1, characterized by co-extruding a polyolefin support layercomprising a vegetable fiber filler and a covering layer of a polyolefinbased thermoplastic elastomer.
 6. A method according to claims 1,wherein said support material is produced by impregnating andcalendering at least one long-fiber mat (6,6′) with an extruded layer ofthermoplastic material (7).
 7. A method according to claim 1, whereinsaid support material and/or said covering material are obtained byreactive extrusion.
 8. An apparatus for the production of autovehicletrim panels, comprising an extruder (5, 10) configured to extrudesupport material (7, 10 a), an extruder (9) configured to extrudecovering material, at least one calendar (8, 12) arranged and configuredto bond together said extruded materials and a press (14) configured tothermoform multilayer sheets of the extruded materials that were boundtogether by said calendar (5) said at least one calendar (8, 12) beingarranged downstream of both of said extruders (5, 10, 9) to receive theextruded material from both of said extruders, said press being arrangeddownstream of said at least one calendar (8, 12) to receive the boundtogether extruded materials from said at least one calendar.
 9. Anapparatus according to claim 8, characterized in that the calender (8)is configured for impregnation of long-fibers mat with a polyolefin. 10.A multi-layer element as obtainable with the method according to claim1.
 11. A mulit-layer element according to claim 10, wherein saidamorphous material is within the range of 60%-100% (w/w) of saidcovering layer.
 12. A trim for vehicles as obtainable with the methodaccording to claim
 1. 13. A method according to claim 1, characterizedby extruding the amorphous thermoplastic material and joining at leastone long-fiber mat with the amorphous thermoplastic material, said layerof support material including said at least one long-fiber mat.